1. Field of the Invention
The invention relates to electronic package technology, and in particular, to a package module having a flexible heat spreader capable of reducing thermal stress and increasing heat dissipation.
2. Description of the Related Art
Demand for small, high performance portable electronic products such as mobile phones, portable computers, and the like have driven the industry to increase integration on semiconductor dice. Accordingly, the industry is achieving high integration by turning to 3D packaging by combining assembly technologies including wire bonding or flip chip to stack die packages to form a multi-package module (MPM).
MPM, a current assembly technology, integrates different dice functions, such as microprocessors or memory, logic, optic ICs, instead of placing individual packages onto a large printed circuit board (PCB). MPM, however, has a much higher power density than an individual single die package. Thus, thermal management is a key factor for successful development.
Conventional methods to combat the presence of heat during device operation typically include providing a heat spreader in thermal contact with IC chips in the package module. FIG. 1 illustrates a conventional electronic device with an MPM. The electronic device comprises an MPM 100 comprising a substrate 12 and mounted on a PCB 101. The upper and lower surfaces of the substrate 12 have dice 16 and 14 with different functions thereon, respectively, to create the MPM 100. The lower surface of the substrate 12 comprises a plurality of bumps 10 thereon to correspondingly connect to the bonding pads 11 on the PCB 101 for electrical connection between the dice 16 and 14 and the PCB 101. In the MPM 100, heat generated from the die 16 can be dissipated by a heat spreading device. For example, a heat spreader 20 contacts the upper surface of the die 16 through an adhesion layer 17. Moreover, a stiffener 18 is disposed on the substrate 12 and surrounds the die 16. The heat spreader 20 and the substrate 12 are fixed by the stiffener 18 through adhesion layers 15 and 17, in which the stiffener 18 serves as a hold for the heat spreader 20.
In such an electronic device, the gap between the die 14 and the PCB 101 is too narrow, however, to dissipate the generated heat from the die 14. Accordingly, low power chips are typically disposed on the lower surface of the substrate, thus hindering circuit design flexibility. Moreover, since the heat spreader 20 and the stiffener 18 typically comprise rigid materials, delamination of the heat spreader 20 and crack of the dice 16 may be occur due to the thermal stress generated from the thermal processes. Thus, device reliability is reduced. Additionally, MPMs with different sizes require stiffeners with different sizes, increasing manufacturing costs.
Accordingly, there is a need to develop a package module with an efficient heat spreader that does not suffer from the deficiencies found in the prior art.